Abstract:

In this paper，the grade of water ecosystem security in Poyang Lake was confirmed by analyzing social economical and water ecological information，using PressureStateResponse (PSR) model，AHP and Composite index methods.Results showed that the indicators such as sanitary sewage processing rate，chemical fertilizer quantity，million GDP water consumption，water quality in Poyang Lake and 〖WTBX〗Oncomelania acreage，etc，had considerable influence on water ecosystem in Poyang Lake.The water ecosystem security value in Poyang Lake in 2005 was 0513 3，which meant “basically safe”.And the value would be 0565 1 in 2010 according to the prediction，higher than that in 2005 but still belonged to “basically safe”.In the near future，the water ecosystem security value in Poyang Lake would fluctuate within “basically safe”.With the social economical development of the lake surrounding area and the increasing environmental pressure，the changing trend of water ecosystem security in Poyang Lake would not be optimistic if the protection efforts are maintained at the present level.Lack of response measures to environmental pressure and deficiency of active awareness and action to protect water ecosystem are the main reasons that lead to the low security grade in Poyang Lake.

Key words: Poyang Lake/ water ecosystem,security evaluation/indicator system/ PSR model/ AHP method